A right-angled triangle has perpendicular sides of length 6cm and 8cm, and a hypoteneuse of 2y cm. Find the length of y.

By Pythagoras' Theorem:(2y)²= 6² + 8²4y² = 36 +64y² = 9 + 16y² = 25y = ±5However, dimensions can only have a positive value. Therefore y=5